Pixel structure and display device including the pixel structure

ABSTRACT

A pixel structure, a display device, and a method of manufacturing a pixel structure, the pixel structure including a base substrate; at least one first electrode arranged in an upper portion of the base substrate; at least one second electrode having a circular shape extending along a circumferential direction around the at least one first electrode; and a plurality of LED elements connected to the first and second electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application based on pending application Ser. No.16/299,735, filed Mar. 12, 2019, which in turn is a continuation ofapplication Ser. No. 15/622,524, filed Jun. 14, 2017, now U.S. Pat. No.10,249,603 B2, issued Apr. 2, 2019, the entire contents of which ishereby incorporated by reference.

Korean Patent Application No. 10-2016-0073837, filed on Jun. 14, 2016,in the Korean Intellectual Property Office, and entitled: “PixelStructure, Display Device Including the Pixel Structure, and Method ofManufacturing the Pixel Structure,” is incorporated by reference hereinin its entirety.

BACKGROUND 1. Field

Embodiments relate to a pixel structure, a display device including thepixel structure, and a method of manufacturing the pixel structure.

2. Description of the Related Art

A light-emitting diode (LED) element may have high photoelectricconversion efficiency, low energy consumption, and a semi-permanentlifetime, and may also be environmentally friendly. The LED element maybe used for, e.g., signal lights, mobile phones, automobile headlights,outdoor electronic scoreboards, liquid crystal display (LCD) back lightunits (BLU), indoor/outdoor lighting devices, etc.

To utilize the LED element in a lighting device or a display, the LEDelement may be connected to an electrode capable of applying power tothe LED element.

SUMMARY

The embodiments may be realized by providing a pixel structure includinga base substrate; at least one first electrode arranged in an upperportion of the base substrate; at least one second electrode having acircular shape extending along a circumferential direction around the atleast one first electrode; and a plurality of LED elements connected tothe first and second electrodes.

The pixel structure may further include a driving transistorelectrically connected to the at least one first electrode; and a powerwiring electrically connected to the at least one second electrode.

The pixel structure may include a plurality of the first electrodes, aplurality of the second electrodes, and an electrode line connecting theplurality of the second electrodes to each other.

A separation distance between the at least one first electrode and theat least one second electrode may be about 1 μm to about 7 μm.

The at least one second electrode may include a first sub-secondelectrode and a second sub-second electrode, the first sub-secondelectrode and second sub-second electrode each having a semicircularshape, and the first sub-second electrode and the second sub-secondelectrode may be spaced apart from each other.

The pixel structure may further include a driving transistorelectrically connected to the first electrode; and a power wiringrespectively electrically connected to the first sub-second electrodeand second sub-second electrode.

The pixel structure may include a plurality of the first electrodes, aplurality of the second electrodes, a first electrode line connecting aplurality of the first sub-second electrodes to each other; and a secondelectrode line connecting a plurality of the second sub-secondelectrodes to each other.

A separation distance between the first sub-second electrode and onefirst electrode may be different from a separation distance between thesecond sub-second electrode and the one first electrode.

The separation distances may each independently be about 1 μm to about 7μm.

The embodiments may be realized by providing a display device includingthe pixel structure according to an embodiment; and a driving circuitconnected to the pixel structure.

The embodiments may be realized by providing a method of manufacturing apixel structure, the method including applying a plurality of LEDelements and a solvent on at least one first electrode and at least onesecond electrode, the at least one second electrode having a circularshape extending along a circumferential direction around the at leastone first electrode; respectively applying different voltages to the atleast one first electrode and the at least one second electrode; andaligning the LED elements between the at least one first electrode andthe at least one second electrode.

A separation distance between the at least one first electrode and theat least one second electrode may be about 1 μm to about 7 μm, and adifference between voltages applied to the at least one first electrodeand the at least one second electrode may be about 10 V to about 50 V.

Applying different voltages to the at least one first electrode and theat least one second electrode may include radially generating a firstelectric field around the at least one first electrode and between theat least one first electrode and the at least one second electrode.

The at least one first electrode may include a plurality of firstelectrodes, the at least one second electrode may include a plurality ofsecond electrodes, a same voltage may be applied to each of the firstelectrodes, and a same voltage may be applied to each of the secondelectrodes.

The at least one second electrode may include at least one firstsub-second electrode and at least one second sub-second electrode, theat least one first sub-second electrode and the at least one secondsub-second electrode each having a semicircular shape, and the at leastone first sub-second electrode and the at least one second sub-secondelectrode may be spaced apart from each other.

The at least one first electrode may include a plurality of firstelectrodes, the at least one first sub-second electrode may include aplurality of first sub-second electrodes, the at least one secondsub-second electrode may include a plurality of second sub-secondelectrodes, and applying different voltages to the at least one firstelectrode and the at least one second electrode may include applying asame voltage to each of the first electrodes, and applying a samevoltage to each of the first sub-second electrodes, and applying a samevoltage to each of the second sub-second electrodes, and wherein thevoltage applied to the first sub-second electrodes may be different fromthe voltage applied to the second sub-second electrodes.

A first sub-electric field may be generated between the at least onefirst electrode and the at least one first sub-second electrode, asecond sub-electric field may be generated between the at least onefirst electrode and the at least one second sub-second electrode, and afirst electric field, as a combination of the first sub-electric fieldand the second sub-electric field, may be radially generated around theat least one first electrode.

A second electric field may be generated between one first sub-secondelectrode and one second sub-second electrode of an adjacent pixelstructure.

A separation distance between the at least one first sub-secondelectrode and the at least one first electrode may be different from aseparation distance between the at least one second sub-second electrodeand the at least one first electrode.

The separation distances may each independently be about 1 μm to about 7μm, a voltage difference between the first electrode and the firstsub-second electrode may be about 10 V to about 50 V, and a voltagedifference between the first electrode and the second sub-secondelectrode may be about 10 V to about 50 V.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will be apparent to those of skill in the art by describing indetail exemplary embodiments with reference to the attached drawings inwhich:

FIG. 1 illustrates a perspective view of a pixel structure according toan embodiment;

FIG. 2A illustrates an enlarged perspective view of a pixel structureaccording to an embodiment;

FIG. 2B illustrates a cross-sectional view taken along line A-A′ of thepixel structure of FIG. 1;

FIG. 3 illustrates a perspective view of an LED element according to anembodiment;

FIG. 4A illustrates a perspective view of a pixel structure according toan embodiment;

FIG. 4B illustrates an enlarged plan view of an electrode structureaccording to an embodiment;

FIG. 4C illustrates a perspective view of a pixel structure according toan embodiment;

FIG. 4D illustrates an enlarged plan view of a pixel structure accordingto an embodiment;

FIG. 5A illustrates a perspective view of a pixel structure according toanother embodiment;

FIG. 5B illustrates a cross-sectional view taken along lines B-B′ of thepixel structure of FIG. 5A;

FIG. 6A illustrates a perspective view of a pixel structure according toanother embodiment;

FIG. 6B illustrates an enlarged plan view of an electrode structureaccording to another embodiment;

FIG. 6C illustrates a perspective view of a pixel structure according toanother embodiment;

FIG. 6D illustrates an enlarged plan view of a pixel structure accordingto another embodiment; and

FIG. 7 illustrates a conceptual diagram of a display device according toan embodiment.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orelement, it can be directly on the other layer or element, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

As used herein, the terms “or” and “and/or” include any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

It will be understood that although the terms “first”, “second”, etc.may be used herein to describe various components, these componentsshould not be limited by these terms. These components are only used todistinguish one component from another.

An expression used in the singular encompasses the expression of theplural, unless it has a clearly different meaning in the context.

It will be further understood that the terms “includes,” “including,”“comprises,” and/or “comprising” used herein specify the presence ofstated features or components, but do not preclude the presence oraddition of one or more other features or components.

FIG. 1 illustrates a perspective view of a pixel structure 1 accordingto an embodiment. FIG. 2A illustrates an enlarged perspective view of apixel structure according to an embodiment. FIG. 2B illustrates across-sectional view taken along line A-A′ of the pixel structure ofFIG. 1. FIG. 3 illustrates a perspective view of an, e.g., extremelysmall-sized, LED element 40 according to an embodiment.

Referring to FIGS. 1 to 3, the pixel structure 1 according to anembodiment may include a base substrate 10, at least one first electrode21 arranged in an upper portion of the base substrate 10, at least onesecond electrode 22 arranged in an upper portion of the base substrate10, an, e.g., extremely small-sized, LED element 40, and a solvent 50. Aplurality of the pixel structures 1 may be arranged on a display area ofa display device 1000 (see FIG. 7) described below. In animplementation, the solvent may be removed after forming the pixelstructure, and may not remain in the pixel structure.

The base substrate 10, on which the first and second electrodes 21 and22 are arranged, may be, e.g., a glass substrate, a crystal substrate, asapphire substrate, a plastic substrate, or a bendable flexible polymerfilm. An area of the base substrate 10 according to an embodiment mayvary according to an area of the first and second electrodes 21 and 22arranged in the upper portion of the base substrate 10 and a size andthe number of the LED elements 40, which will be described below,arranged between the first and second electrodes 21 and 22.

A buffer layer 601 may further be included in the upper portion of thebase substrate 10. The buffer layer 601 may help reduce the possibilityof and/or prevent ion impurities from being diffused into the uppersurface of the base substrate 10 and may also help reduce and/or preventmoisture or outside air from permeating into the upper surface of thebase substrate 10 and may flatten a surface of the same. In animplementation, the buffer layer 601 may include an inorganic materialsuch as silicon oxide, silicon nitride, silicon oxy-nitride, aluminumoxide, aluminum nitride, titanium oxide or titanium nitride, an organicmaterial such as polyimide, polyester or acryl, or a laminate thereof.In an implementation, the buffer layer 601 may be omitted. The bufferlayer 601 may be formed by various deposition methods, e.g., a plasmaenhanced chemical vapor deposition (PECVD) method, an atmosphericpressure CVD (APCVD) method, or a low pressure CVD (LPCVD) method.

The first thin film transistor TFT1 may be a driving thin filmtransistor for driving the LED element 40 and may include a first activelayer 611, a first gate electrode 612, a first drain electrode 613, anda first source electrode 614. A first gate insulating film 602 may beinterposed between the first gate electrode 612 and the first activelayer 611 to insulate them from each other. The first gate electrode 612may be formed on the first gate insulating film 602 to overlap a part ofthe first active layer 611.

The second thin film transistor TFT2 may include a second active layer621, a second gate electrode 622, a second drain electrode 623, and asecond source electrode 624. A first gate insulating film 602 may beinterposed between the second gate electrode 622 and the second activelayer 621 to insulate them from each other.

The first and second active layers 611 and 621 may be formed on thebuffer layer 601. An inorganic or organic semiconductor such asamorphous-silicon or poly-silicon may be used for the first and secondactive layers 611 and 621. In an implementation, the first active layer611 may be formed of an oxide semiconductor. For example, the oxidesemiconductor may include an oxide of a material selected from metalelements of groups 12, 13, and 14, such as zinc (Zn), indium (In),gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge), and hafnium (Hf),and a combination thereof.

The first gate insulating film 602 may be provided on the buffer layer601 and may cover the first and second active layers 611 and 621. Thesecond gate insulating film 603 may cover the first and second gateelectrodes 612 and 622.

Each of the first and second gate electrodes 612 and 622 may include asingle film such as gold (Au), silver (Ag), copper (Cu), nickel (Ni),platinum (Pt), palladium (Pd), aluminum (Al), molybdenum (Mo) orchromium (Cr), a multilayer film, or an alloy such as Al:Nd or Mo:W.

The first and second gate insulating films 602 and 603 may include aninorganic film such as silicon oxide, silicon nitride or metal oxide,and may be formed of a single layer or a multi-layer.

An interlayer insulating film 604 may be formed on the second gateinsulating film 603. The interlayer insulating film 604 may be formed ofan inorganic film such as silicon oxide or silicon nitride. Theinterlayer insulating film 604 may include an organic film.

Each of the first drain electrode 613 and the first source electrode 614may be formed on the interlayer insulating film 604. Each of the firstdrain electrode 613 and the first source electrode 614 may contact thefirst active layer 611 through a contact hole. Furthermore, each of thesecond drain electrode 623 and the second source electrode 624 may beformed on the interlayer insulating film 604, and each of the seconddrain electrode 623 and the second source electrode 624 may contact thesecond active layer 621 through the contact hole. Each of the first andsecond drain electrodes 613 and 623, and the first and second sourceelectrodes 614 and 621 may include a metal, an alloy, metal nitride,conductive metal oxide, a transparent conductive material, and so on.

In an implementation, the thin film transistors TFT1 and TFT2 may have atop gate structure or a bottom gate structure in which the first gateelectrode 612 is arranged under the first active layer 611 may also bepossible.

A planarization film 605 may cover the thin film transistors TFT1 andTFT2 and may be provided on the interlayer insulating film 604. Theplanarization film 605 may flatten the interlayer insulating film 604 toimprove a luminous efficiency of the LED element 40 to be formed on theplanarization film 605. In an implementation, the planarization film 605may include a through hole exposing a part of the first drain electrode613.

The planarization film 605 may be formed of an insulator. For example,the planarization film 605 may include inorganic materials, organicmaterials, or a combination of organic/inorganic materials, may beformed in a structure of a monolayer or a multilayer, and may be formedvia various deposition methods. In an implementation, the planarizationfilm 605 may include at least one of a polyacrylate resin, an epoxyresin, a phenolic resin, a polyamide resin, a polyimide resin, anunsaturated polyester resin, a polyphenylene resin, a polyphenylenesulfide resin, and benzocyclobutene (BCB).

In an implementation, any one of the interlayer insulating film 604 andthe planarization film 605 may be omitted.

The first electrode 21 may be arranged in an upper portion of theinterlayer insulating film 605 and may be electrically connected to theLED element 40. For example, the first electrode 21 may include aplurality of the first electrodes 21 that may be arranged in the upperportion of the interlayer insulating film 605. The plurality of thefirst electrodes 21 may be spaced apart from each other with aprescribed gap therebetween.

Furthermore, the first electrode 21 according to an embodiment may beelectrically connected to the first drain electrode 613 and may receivepower. In this case, the first drain electrode 613 may be connected tothe first electrode 21 via the through hole exposing a part of the firstdrain electrode 613.

In an implementation, the first electrode 21 according to an embodimentmay include at least one metal of Al, titanium (Ti), In, Au, and Ag, orat least one transparent material of indium tin oxide (ITO), zinc oxide(ZnO):Al, and a carbon nanotube (CNT)-conductive polymer composite. Whenthe first electrode 21 includes at least two types of materials, thefirst electrode 21 according to an embodiment may have a structure inwhich two or more materials of different types are laminated.

The second electrode 22 may be arranged in the upper portion of theinterlayer insulating film 605 and may be electrically connected to theLED element 40. For example, the second electrode 22 may have a circularor annular shape (e.g., in plan view) extending along a circumferentialdirection around the first electrode 21. In this case, the first andsecond electrodes 21 and 22 may be spaced apart from each other with aprescribed gap therebetween, e.g., a first separation distance D₁ (seeFIG. 4B) therebetween.

In an implementation, the second electrode 22 may include a plurality ofthe second electrodes 22 on the upper portion of the base substrate 10.The plurality of the second electrodes 22 may be spaced apart from eachother with a prescribed gap therebetween. In an implementation, thesecond electrodes 22 may be connected to each other via an electrodeline 220. In this case, a power wiring 630 may be electrically connectedto the second electrode 22 via a through hole, and accordingly, thesecond electrodes 22 may receive an identical or same voltage power fromthe power wiring 630. For example, a planarization film 640 to flatten asurface of the power wiring 630 may be arranged under the power wiring630. In an implementation, the planarization film 640 may be omitted.

In an implementation, the second electrode 22 may include at least onemetal of Al, Ti, In, Au, and Ag, or at least one transparent material ofITO, ZnO:Al, and a CNT-conductive polymer composite. When the secondelectrode 22 includes at least two materials, the second electrode 22according to an embodiment may have a structure in which two or morematerials of different types are laminated. For example, materialsincluded in the first and second electrodes 21 and 22 may be the same ordifferent from each other.

In an implementation, the LED element 40, which is a light-emittingelement from which light is emitted, may have various shapes, e.g., acolumn or rod shape or a rectangular parallelepiped. As illustrated inFIG. 3, the LED element 40 according to an embodiment may include afirst electrode layer 410, a second electrode layer 420, a firstsemiconductor layer 430, a second semiconductor layer 440, and an activelayer 450 arranged between the first and second semiconductor layers 430and 440. For example, the first electrode layer 410, the firstsemiconductor layer 430, the active layer 450, the second semiconductorlayer 440, and the second electrode layer 420 may be sequentiallylaminated along a length direction of the LED element 40. In animplementation, a length T of the LED element 40 may be, e.g., about 2μm to 5 μm.

Each of the first and second electrode layers 410 and 420 may be anohmic contact electrode. In an implementation, each of the first andsecond electrode layers 410 and 420 may be a Schottky contact electrode.Each of the first and second electrode layers 410 and 420 may include aconductive metal. For example, each of the first and second electrodelayers 410 and 420 may include at least one metal of Al, Ti, In, Au, andAg. In an implementation, each of the first and second electrode layers410 and 420 may include identical materials. In an implementation, thefirst and second electrode layers 410 and 420 may include materialsdifferent from each other.

The first semiconductor layer 430 according to an embodiment mayinclude, e.g., an n-type semiconductor layer. In an implementation, whenthe LED element 40 is a blue light-emitting element, the n-typesemiconductor layer may include a semiconductor material having acomposition formula of In_(x)Al_(y)Ga_(1-x-y)N (0≤x≤1, 0≤y≤1, 0≤x+y≤1),e.g., one of InAlGaN, GaN, AlGaN, InGaN, AlN, and InN, and the n-typesemiconductor layer may be doped with a first conductive dopant (e.g.,silicon (Si), Ge, or Sn). In an implementation, the LED element 40 mayinclude a different type of group III-V semiconductor material in then-type semiconductor layer when a light emission color of the LEDelement 40 is not blue. In an implementation, the first electrode layer410 may not be an ohmic contact electrode or may be omitted. In animplementation, the first semiconductor layer 430 may be connected(e.g., directly connected) to the first electrode 21.

The second semiconductor layer 440 according to an embodiment mayinclude, e.g., a p-type semiconductor layer. In an implementation, whenthe LED element 40 is a blue light-emitting element, the p-typesemiconductor layer may include a semiconductor material having acomposition formula of In_(x)Al_(y)Ga_(1-x-y)N, e.g., one of InAlGaN,GaN, AlGaN, InGaN, AlN, and InN, and the p-type semiconductor layer maybe doped with a second conductive dopant (e.g., magnesium (Mg)). In animplementation, the second electrode layer 420 may not be an ohmiccontact electrode or may be omitted. In an implementation, the secondsemiconductor layer 440 may be connected (e.g., directly connected) tothe second electrode 22.

The active layer 450 may be arranged between the first and secondsemiconductor layers 430 and 440, and may have, e.g., a single ormultiple quantum well structure. For example, a clad layer doped with aconductive dopant may be arranged in an upper portion and/or lowerportion of the active layer 450, and the clad layer doped with theconductive dopant may be realized as an AlGaN layer or InAlGaN layer. Inan implementation, materials such as AlGaN or AlInGaN may also beincluded in the active layer 450. When an electric field is applied tothe active layer 450, light may be generated due to coupling of anelectronic-hole pair, and a location of the active layer 450 may varyaccording to types of LED elements. In an implementation, the LEDelement 40 may include a different type of group III-V semiconductormaterial in the active layer 450 when a light emission color of the LEDelement 40 is not blue. In an implementation, the first and secondsemiconductor layers 430 and 440 and the active layer 450 may beincluded in the LED element 40. In an implementation, the LED element 40may further include a phosphor layer, an active layer, a semiconductorlayer and/or electrode layer in upper portions and lower portions of thefirst and second semiconductor layers 430 and 440.

In an implementation, the LED element 40 may further include aninsulating film 470 covering an outer surface of the active layer 450.For example, the insulating film 470 may cover a side surface of theactive layer 450, and thus, an electrical short-circuit, which may begenerated when the active layer 450 contacts the first electrode 21 orthe second electrode 22, may be reduced and/or prevented. The insulatingfilm 470 may help prevent a reduction in luminous efficiency byprotecting an outer surface, which includes the active layer 450, of theLED element 40.

The solvent 50, a moving medium for activating dispersion and movementof the LED element 40 according to an embodiment, may be used. In animplementation, the solvent 50 may vaporize easily and may notphysically and/or chemically damage the LED element 40. In animplementation, the solvent 50 may include, e.g., acetone, water,alcohol, or toluene.

In an implementation, the solvent 50 may be input or provided to the LEDelement 40 in a prescribed weight ratio. Maintaining the solvent 50within a desired range may help reduce the possibility of and/or preventexcess amounts of the solvent 50 from being diffused to areas other thana region of the first and second electrodes 21 and 22 desired by the LEDelement 40, thereby helping to prevent an undesirable reduction in thenumber of the LED elements 40 to be mounted in a mounting regionaccording to the first and second electrodes 21 and 22. Maintaining thesolvent 50 within a desired range may help ensure that sufficientsolvent is present to facilitate movement or alignment of each of theLED elements 40.

As described above, a prescribed power may be applied to the first andsecond electrodes 21 and 22 via the first drain electrode 613 and thepower wiring 630. For example, the first drain electrode 613 may beconnected to the first electrode 21 and may apply power to the same, andthe power wiring 630 may be connected to the second electrode 22 and mayapply power to the same. Accordingly, an electric field E may be formedbetween the first and second electrodes 21 and 22. Here, power having aprescribed amplitude and period may be respectively applied to the firstand second electrodes 21 and 22 by respectively applying alternatingcurrent (AC) power having a prescribed amplitude and period or byrepeatedly applying direct current (DC) power to the first and secondelectrodes 21 and 22. Hereinafter, self-alignment of the LED element 40will be described in more detail, in which the self-alignment of the LEDelement 40 may be performed by the electric field E formed by applyingprescribed power to the first and second electrodes 21 and 22.

FIG. 4A illustrates a perspective view of the pixel structure 1 beforevoltage is applied to the first and second electrodes 21 and 22,according to an embodiment. FIG. 4B illustrates an enlarged plan view ofan electrode structure according to an embodiment (e.g., before voltageis applied to the first and second electrodes 21 and 22). FIG. 4Cillustrates a perspective view of the pixel structure 1 after voltage isapplied to the first and second electrodes 21 and 22, according to anembodiment. FIG. 4D illustrates an enlarged plan view of an electrodestructure according to an embodiment (e.g., after voltage is applied tothe first and second electrodes 21 and 22).

The LED element 40 according to an embodiment may be of an extremelysmall nano-size, and it may be difficult to physically or directlyconnect the LED element 40 to the first and second electrodes 21 and 22.Referring to FIG. 4A, the LED element 40 according to an embodiment maybe input or provided to the first and second electrodes 21 and 22 in asolution or dispersion state where the LED element 40 is mixed ordispersed in the solvent 50. Here, when power is not supplied to thefirst and second electrodes 21 and 22, a plurality of the LED elements40 may float or be dispersed in the solution, and may be arranged, e.g.,only in contours of the first and second electrodes 21 and 22 orarranged adjacent to each other. In an implementation, when the LEDelement 40 is cylindrical or rod shaped, the LED element 40 may move onthe first and second electrodes 21 and 22 while rotating due to shapecharacteristics. Thus, the LED element 40 may not be simultaneouslyconnected to the first and second electrodes 21 and 22 by aself-alignment method.

Referring to FIGS. 2A, 2B, and 4B, power of different voltages may berespectively applied to the first and second electrodes 21 and 22according to an embodiment, and thus, a prescribed electric field E maybe formed between the first and second electrodes 21 and 22. Forexample, as described above, when the AC power or the DC power having aprescribed amplitude and period is repeatedly applied to the first andsecond electrodes 21 and 22 several times through the first drainelectrode 613 and power wiring 630, a radial first electric field E₁(according to a potential difference of the first and second electrodes21 and 22) may be formed between the first and second electrodes 21 and22. Here, a strength of the first electric field E₁ may be proportionalto the potential difference of the first and second electrodes 21 and22, and may be inversely proportional to a first separation distance D₁between the first and second electrodes 21 and 22. In an implementation,the first separation distance D₁ between the first and second electrodes21 and 22 may be about 1 μm to about 7 μm. In an implementation, avoltage difference between the first and second electrodes 21 and 22 maybe about 10 V to about 50 V.

Referring to FIGS. 4C and 4D, when power is supplied to the first andsecond electrodes 21 and 22, the LED element 40 according to anembodiment may be aligned, e.g., self-aligned, between the first andsecond electrodes 21 and 22 by inductance of the first electric field E₁which is formed by the potential difference of the first and secondelectrodes 21 and 22. As described above, the first electric field E₁ ina radiation direction around the first electrode 21 may be formed due tothe potential difference of the first and second electrodes 21 and 22,and charge may be asymmetrically induced to the LED element 40 byinductance of the first electric field E₁. Therefore, the LED element 40may be aligned, e.g., self-aligned, between the first and secondelectrodes 21 and 22 along the first electric field E₁. Here, connectorsof the LED element 40, e.g., the first and second electrode layers 410and 420 may be respectively arranged to simultaneously contact the firstand second electrodes 21 and 22. Thus, the LED element 40 may beelectrically connected to the first and second electrodes 21 and 22. TheLED element 40 according to an embodiment may be aligned, e.g.,self-aligned, between the first and second electrodes 21 and 22 byinductance of an electric field E (which is formed by the potentialdifference of the first and second electrodes 21 and 22), and the numberof the LED element 40 connected to the first and second electrodes 21and 22 may increase as strength of the electric field E is greater. Inan implementation, the strength of the electric field E may beproportional to the potential difference of the first and secondelectrodes 21 and 22, and may be inversely proportional to the firstseparation distance D₁ between the first and second electrodes 21 and22.

Hereinafter, in order to form pixel regions in which a plurality of theLED elements 40 are substantially mounted, an insulation process toinsulate remaining regions (e.g., excluding or other than the region ofthe first and second electrodes 21 and 22 in which the LED elements 40are substantially mounted) may be performed. Accordingly, the pixelstructure 1 including a plurality of the first and second electrodes 21and 22 may include a plurality of pixel regions.

A display device including a plurality of the LED elements 40 may beclassified into a passive-matrix type display device and anactive-matrix type display device according to a method of driving theLED element 40. For example, when the display device is an active-matrixtype, the pixel structure 1 may include the first thin film transistorTFT1 as a driving transistor controlling the amount of current suppliedto the LED element 40, and the second thin film transistor TFT2 as aswitching transistor transmitting a data voltage to the first thin filmtransistor TFT1, as in the embodiment described above. An active-matrixtype display device selectively turning on unit pixels in resolution,contrast ratio, and operating speed points of view is mainly usedrecently. In an implementation, a passive-matrix type display deviceturning on pixels by group may also be possible by using the electrodearrangement according to an embodiment.

As described above, the pixel structure 1 according to an embodiment mayalign and connect a plurality of the LED elements 40, which may benano-sized and independently manufactured, between the first and secondelectrodes 21 and 22, by using the electric field E radially formedbetween the first and second electrodes 21 and 22. Thus, coupling theLED element 40 with the first and second electrodes 21 and 22 inone-to-one correspondence may be facilitated. Furthermore, even when acylindrical LED element 40 is used, a defect rate of the pixel structure1 may be minimized as the alignment between the LED element 40 and thefirst and second electrodes 21 and 22 may be maintained. Furthermore, itis possible to intensively arrange and connect the LED element 40 at adesired mounting region including the first and second electrodes 21 and22 that are different from each other.

FIG. 5A illustrates a perspective view of the pixel structure 1according to another embodiment. FIG. 5B illustrates a cross-sectionalview taken along lines B-B′ of the pixel structure 1 of FIG. 5A.Referring to FIGS. 5A and 5B, the pixel structure 1 according to anotherembodiment may include a first electrode 21 arranged in the upperportion of the base substrate 10, a second electrode 22 (including afirst sub-second electrode 22-1 and a second sub-second electrode 22-2),a plurality of the LED elements 40 arranged among the first electrode21, the first sub-second electrode 22-1, and the second sub-secondelectrode 22-2, and a solvent 50 (in which the LED elements 40 are mixedor dispersed). A duplicate description will be omitted for simplicity.In an implementation, after forming the pixel structure, the solvent 50may be removed and may not remain in the pixel structure.

The second electrode 22 may include the first sub-second electrode 22-1and the second sub-second electrode 22-2 spaced apart from each other.The first sub-second electrode 22-1, and the second sub-second electrode22-2 may be arranged in the upper portion of the interlayer insulatingfilm 605 and may be electrically connected to the LED element 40. Forexample, each of the first sub-second electrode 22-1, and the secondsub-second electrode 22-2 may have a semicircular shape extending alonga circumferential direction around the first electrode 21.

In an implementation, the first sub-second electrode 22-1 and the secondsub-second electrode 22-2 may include a plurality of the firstsub-second electrodes 22-1 and a plurality of the second sub-secondelectrodes 22-2 arranged in the upper portion of the interlayerinsulating film 605 to be spaced apart from each other with a prescribedgap therebetween. In an implementation, the first sub-second electrodes22-1 may be connected to each other via a first electrode line 220-1. Asillustrated in FIG. 5B, the power wiring 630 may be electricallyconnected to each of the first sub-second electrodes 22-1 and the secondsub-second electrodes 22-2 via a through hole. Accordingly, power of afirst voltage may be supplied to the first sub-second electrodes 22-1and power of a second voltage may be supplied to the second sub-secondelectrodes 22-2. A size or voltage of the first voltage may be differentfrom that of the second voltage.

In an implementation, the first sub-second electrodes 22-1 and thesecond sub-second electrodes 22-2 may each independently include atleast one metal of Al, Ti, In, Au, and Ag, or at least one transparentmaterial of ITO, ZnO:Al, and a CNT-conductive polymer composite. Wheneach of the first sub-second electrodes 22-1 and the second sub-secondelectrodes 22-2 includes at least two materials, each of the firstsub-second electrodes 22-1 and the second sub-second electrodes 22-2 mayhave a structure in which two or more materials of different types arelaminated. In an implementation, the first sub-second electrodes 22-1and the second sub-second electrodes 22-2 may include differentmaterials as well as an identical material.

FIG. 6A illustrates a perspective view of the pixel structure 1 beforevoltage is applied to the first and second electrodes 21 and 22,according to another embodiment. FIG. 6B illustrates an enlarged planview of the pixel structure 1 according to the embodiment. FIG. 6Cillustrates a perspective view of the pixel structure 1 after voltage isapplied to the first and second electrodes 21 and 22, according to theembodiment. FIG. 6D illustrates an enlarged plan view of the pixelstructure 1 according to the embodiment.

As illustrated in FIGS. 4A to 4D, the pixel structure 1 according to anembodiment may align and connect a plurality of the LED elements 40,which may be nano-sized and independently manufactured, between thefirst and second electrodes 21 and 22, by using the electric field Eradially formed between the first and second electrodes 21 and 22.Therefore, when the first electric field E₁ is radially formed betweenthe first and second electrodes 21 and 22 as illustrated in FIG. 4C, theLED element 40 may be aligned between the first and second electrodes 21and 22, and a separate electric field E may not be formed between aplurality of the second electrodes 22 (e.g., adjacent second electrodes22) because the same voltage may be applied to the second electrodes 22.Accordingly, the LED element 40 between the second electrodes 22 may bearranged in contours of the second electrodes 22 or arranged adjacent toeach other.

Referring to FIG. 6A, the LED element 40 according to an embodiment maybe input or provided to the first electrode 21, the first sub-secondelectrode 22-1, and the second sub-second electrode 22-2 in a solutionor dispersion state where the LED element 40 is mixed or dispersed inthe solvent 50. When power is not supplied to the first electrode 21,the first sub-second electrode 22-1, and the second sub-second electrode22-2, a plurality of the LED elements 40 may float or otherwise bedispersed in the solution and may be arranged, e.g., only in contours ofthe first electrode 21, the first sub-second electrode 22-1, and thesecond sub-second electrode 22-2, or may be arranged, e.g., adjacent toone another. Referring to FIG. 6B, power may be applied to each of thefirst electrode 21, the first sub-second electrode 22-1, and the secondsub-second electrode 22-2. Thus, a prescribed electric field E may beformed between the first electrode 21 and the first sub-second electrode22-1, between the first electrode 21 and the second sub-second electrode22-2, and between the first sub-second electrode 22-1 and the secondsub-second electrode 22-2. For example, as described above, when the ACpower or the DC power having a prescribed amplitude and period isrepeatedly applied to the first electrode 21, the first sub-secondelectrode 22-1, and the second sub-second electrode 22-2 several times,a first sub-electric field E₁₁ according to a potential difference ofthe first electrode 21 and the first sub-second electrode 22-1 may beformed between the first electrode 21 and the first sub-second electrode22-1, a second sub-electric field E₁₂ according to the potentialdifference of the first electrode 21 and the second sub-second electrode22-2 may be formed between the first electrode 21 and the secondsub-second electrode 22-2, and a second electric field E₂ according to apotential difference of the first sub-second electrode 22-1 and thesecond sub-second electrode 22-2 may be formed between the firstsub-second electrode 22-1 and the second sub-second electrode 22-2. Forexample, the second electric field E₂ may be formed between the firstsub-second electrode 22-1 of one pixel and the second sub-secondelectrode 22-2 of a different, adjacent pixel.

Referring to FIGS. 6C and 6D, the LED element 40 according to anembodiment may be aligned, e.g., self-aligned, between the firstelectrode 21 and the first sub-second electrode 22-1 by inductance ofthe first sub-electric field E₁₁ which is formed by the potentialdifference of the first electrode 21 and the first sub-second electrode22-1. According to an embodiment, as described above, when power havinga prescribed voltage difference is supplied to the first electrode 21and the first sub-second electrode 22-1, the first sub-electric fieldE₁₁ may be formed between the first electrode 21 and the firstsub-second electrode 22-1 by the potential difference of the firstelectrode 21 and the first sub-second electrode 22-1. Therefore, chargemay be asymmetrically induced to the LED element 40 by the inductance ofthe first sub-electric field E₁₁, and the LED element 40 may be aligned,e.g., self-aligned, between the first electrode 21 and the firstsub-second electrode 22-1 along the first sub-electric field E₁₁. In animplementation, connectors of the LED element 40, e.g., the first andsecond electrode layers 410 and 420, may be respectively arranged tosimultaneously respectively contact the first electrode 21 and the firstsub-second electrode 22-1. Thus, the LED element 40 may be electricallyconnected to the first electrode 21 and the first sub-second electrode22-1.

The LED element 40 may be aligned, e.g., self-aligned, between the firstelectrode 21 and the second sub-second electrode 22-2 by inductance ofthe second sub-electric field E₁₂ (which is formed by the potentialdifference of the first electrode 21 and the second sub-second electrode22-2). The formation of the second sub-electric field E₁₂ by the firstelectrode 21 and the second sub-second electrode 22-2, and thealignment, e.g., self-alignment, of the LED element 40 which isgenerated by charge asymmetrically induced to the LED element 40 by theinductance of the second sub-electric field E₁₂ may be substantially thesame as the alignment, e.g., self-alignment, method of the LED element40 by the first electrode 21 and the first sub-second electrode 22-1,and a repeated description may be omitted for simplicity.

In an implementation, as described above, the first sub-electric fieldE₁₁ (formed by the potential difference of the first electrode 21 andthe first sub-second electrode 22-1 and the second sub-electric fieldE₁₂ formed by the potential difference of the first electrode 21 and thesecond sub-second electrode 22-2 may be radially formed around the firstelectrode 21. Voltages of power applied to each of the first sub-secondelectrode 22-1 and the second sub-second electrode 22-2 may be differentfrom each other, and the first sub-electric field E₁₁ and the secondsub-field E₁₂ may be different from each other as long as a separationdistance D₁₁ between the first electrode 21 and the first sub-secondelectrode 22-1 and a separation distance D₁₂ between the first electrode21 and the second sub-second electrode 22-2 are the same as each other.Therefore, in order to make the first sub-electric field E₁₁ and thesecond sub-electric field E₁₂ (formed among the first electrode 21, thefirst sub-second electrode 22-1, and the second sub-second electrode22-2) uniform, the separation distance D₁₁ and the separation distanceD₁₂ may be formed differently, e.g., may be different distances. Forexample, when a first voltage of power applied to the first sub-secondelectrode 22-1 is greater than a second voltage of power applied to thesecond sub-second electrode 22-2, the separation distance D₁₁ may belarger than the separation distance D₁₂. Thus, the first electric fieldE₁ (e.g., a combination of the first sub-electric field E₁₁ and thesecond sub-electric field E₁₂) may be uniformly formed. In animplementation, the separation distance D₁₁ and the separation distanceD₁₂ may be the same as each other. For example, when length T of the LEDelement 40 is 2 μm to 5 μm as illustrated in FIG. 3, the separationdistance D₁₁ and the separation distance D₁₂ may be each about 1 μm toabout 7 μm, and a voltage difference between the first electrode 21 andthe first sub-second electrode 22-1 and between the first electrode 21and the second sub-second electrode 22-2 may be about 10 V to about 50V.

In an implementation, when the LED element 40 is arranged between thefirst sub-second electrode 22-1 and the second sub-second electrode22-2, the LED element 40 may move to a side of the first sub-secondelectrode 22-1 or the second sub-second electrode 22-2 by inductance ofthe second electric field E₂ (which is formed by the potentialdifference of the first sub-second electrode 22-1 and the secondsub-second electrode 22-2. In an implementation, when a voltage higherthan that of the second sub-second electrode 22-2 is applied to thefirst sub-second electrode 22-1, and a voltage is not applied to thefirst electrode 21, the first sub-electric field E₁₁ may be formedbetween the first electrode 21 and the first sub-second electrode 22-1,the second sub-electric field E₁₂ may be formed between the firstelectrode 21 and the second sub-second electrode 22-2, and the secondelectric field E₂ (toward the second sub-second electrode 22-2 from thefirst sub-second electrode 22-1 may be formed. In an implementation,the, e.g., strength of the, first sub-electric field E₁₁ may be greaterthan the second sub-electric field E₁₂, and the, e.g., strength of the,second sub-electric field E₁₂ may be greater than the second electricfield E₂.

For example, when the LED element 40 is arranged between the firstsub-second electrode 22-1 and the second sub-second electrode 22-2, acharge may be asymmetrically induced to the LED element 40 by theinductance of the second electric field E₂ (formed between the firstsub-second electrode 22-1 and the second sub-second electrode 22-2). TheLED element 40 arranged between the first sub-second electrode 22-1 andthe second sub-second electrode 22-2 may move to the second sub-secondelectrode 22-2 along a direction of the second electric field E₂.Afterwards, the LED element 40 may be aligned, e.g., self-aligned,between the first sub-second electrode 22-1 and the second sub-secondelectrode 22-2 by the second sub-electric field E₁₂ which is formed bythe first electrode 21 and the second sub-second electrode 22-2.

As described above, the pixel structure 1 according to an embodiment mayremove a region where the electric fields E are balanced with each otherby adapting the first sub-second electrode 22-1 and the secondsub-second electrode 22-2 (to which different voltages are respectivelyapplied). Thus, all the LED elements 40 arranged in pixels may bealigned and/or connected to one another among the first electrode 21,the first sub-second electrode 22-1, and the second sub-second electrode22-2.

FIG. 7 illustrates a conceptual diagram of a display device 1000according to an embodiment.

Referring to FIG. 7, the display device 1000 may include a plurality ofthe pixel structures 1 according to the embodiments described above, anddriving circuits connected to the pixel structures 1.

The pixel structures 1 may be arranged in a display area DA of thedisplay device 1000. The driving circuits may be arranged in anon-display area arranged in a contour of the display area DA of thedisplay device 1000. The driving circuits may include a data drivingcircuit 7 and a gate driving circuit 8.

In an implementation, a length of a side of each of the pixel structures1 may be about 600 μm or less. In an implementation, when the pixelstructures 1 form sub pixels, the length of a side of each of the pixelstructures 1 may be about 200 μm or less. A side of each of the pixelstructures 1 may be a short side of each of the pixel structures 1. Inan implementation, sizes of the pixel structures 1 may change accordingto sizes and the number of required pixels of the display device 1000.

The data driving circuit 7 may include a plurality of source driveintegrated circuits (IC) and may drive data lines DL. The gate drivingcircuit 8 may include at least one gate drive IC and may supply a scanpulse to gate lines GL.

By way of summation and review, an arrangement of the LED element andthe electrode may be considered in relation to an objective of use,reduction of a space for the electrode, and a method of manufacturingthe electrode.

A method of arranging the LED element and the electrode may include amethod of directly growing the LED element on the electrode and a methodof arranging the LED element on the electrode after independentlygrowing the LED element. In the latter case, a general three-dimensional(3D) LED element may be connected to the electrode after being erectedin an upright position. It may be difficult to erect upright the LEDelement in an upright position on the electrode when the LED element hasan extremely small nano-size.

The embodiments may provide pixel structures, display devices includingthe pixel structure, and methods of manufacturing the pixel structures,whereby an abnormal misalignment of an extremely small nano-sizedlight-emitting diode (LED) element may be reduced and/or prevented byaligning and connecting a plurality of the LED elements, which areindependently manufactured, between two electrodes.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. A pixel structure comprising: a base substrate; afirst electrode on the base substrate, the first electrode beingcircular; a second electrode having a circular shape of a substantiallyuniform width between an inner edge and an outer edge, and extending ina circumferential direction around the first electrode, the inner edgebeing defined by an inner radius, and the outer edge being defined by anouter radius; and a plurality of LED elements having a rod shape thatare connected to the first electrode and the second electrode, and thatare arranged to extend radially outward from the first electrode and toextend in different directions so that long axes of the plurality of LEDelements have a radial arrangement, wherein the first and secondelectrodes are concentric.
 2. The pixel structure of claim 1, wherein afirst end of each of the plurality of LED elements is located on thefirst electrode and a second end is located on the second electrode. 3.The pixel structure of claim 2, wherein the first end of each of theplurality of LED elements is directly connected to the first electrodeand the second end is directly connected to the second electrode.
 4. Thepixel structure of claim 1, wherein two LED elements adjacent to eachother from among the plurality of LED elements are arranged in a firstdirection and a second direction intersecting the first direction,respectively, wherein the first direction and the second direction forman acute angle.
 5. The pixel structure of claim 1, wherein imaginarylines extending from different directions in which the plurality of LEDelements are arranged respectively meet at a virtual contact point,wherein the virtual contact point is located in the first electrode. 6.The pixel structure of claim 1, wherein the second electrode isannularly provided with a closed curve.
 7. The pixel structure of claim6, wherein the first electrode has a circular shape and is located at acenter of the second electrode.
 8. The pixel structure of claim 1,further comprising: a driving transistor electrically connected to thefirst electrode; and a power wire electrically connected to the secondelectrode.
 9. The pixel structure of claim 1, wherein the firstelectrode and the second electrode are plural, the pixel structurefurther comprising an electrode line connecting the plurality of secondelectrodes.
 10. The pixel structure of claim 1, wherein a separationdistance between the first electrode and the second electrode is 1 μm ormore and 7 μm or less.
 11. The pixel structure of claim 1, wherein thesecond electrode comprises a first sub-electrode and a secondsub-electrode having a semicircular shape, wherein the firstsub-electrode and the second sub-electrode are separated and arranged tobe spaced apart from each other, wherein a first one of the LED elementsis connected to the first electrode and connected to the firstsub-electrode, and wherein a second one of the LED elements is connectedto the first electrode and connected to the second sub-electrode. 12.The pixel structure of claim 11, further comprising: a drivingtransistor electrically connected to the first electrode; and a powerwire electrically connected to the first sub-electrode and the secondsub-electrode.
 13. The pixel structure of claim 11, wherein the firstsub-electrode and the second sub-electrode are plural, the pixelstructure further comprising: a first electrode line connecting theplurality of first sub-electrodes; and a second electrode lineconnecting the plurality of second sub-electrodes.
 14. The pixelstructure of claim 13, wherein a first separation distance between thefirst sub-electrode and the first electrode is different from a secondseparation distance between the second sub-electrode and the firstelectrode.
 15. The pixel structure of claim 14, wherein the firstseparation distance and the second separation distance are 1 μm or moreand 7 μm or less.
 16. The pixel structure of claim 11, wherein a firstend of each of the plurality of LED elements is located on the firstelectrode and a second end is located on the first sub-electrode or thesecond sub-electrode.
 17. The pixel structure of claim 16, wherein thefirst end of each of the plurality of LED elements is directly connectedto the first electrode and the second end is directly connected to thefirst sub-electrode or the second sub-electrode.
 18. A display devicecomprising: the pixel structure of claim 1; and a driving circuitconnected to the pixel structure.